I've seen at least two videos of a jar being used in the wrong way. Using these to make casts is the third because the rigid container will have to be broken to get the mold.

I recommend cleaning it and just using it to store bits and bobs or food if its food-safe. Or just recycle it. Or, make a lego submarine.

Might be a bit narrow, but if you wanted to make some pickle spears it should work.

I like to do a fridge pickle (always gets eaten within a few weeks, so spoilage isn't a huge concern). Something like this pickled jalapeño recipe works with most veggies, and you can use some whole black peppercorn and mustard seeds (or a pickling spice mix) to give it that pickle flavor.

Hot Dogs! Oh…. wait

Make a candle?

Gonna need a longer jar.

Container for smaller objects.

'Fess up, OP - you wouldn't need the whole jar for that.

I have a co-worker who just started pickling his own eggs. He boils and peels them, then puts them in a jar with 1/3 water, 1/3 white vinegar, 1/3 apple cider vinegar, 1 tsp sugar and some pickling spices. I've seen him eat an entire jar for lunch, which makes me grateful my desk is far away from his.

If you don’t always need glass jars to pour your bacon grease before you wash the pan, you are clearly not eating enough bacon

I fill mine with plaster of Paris and cast....oh, yeah I mean, beyond that I don't know what else.

Look into lacto fermentation (home made pickles like real sauerkraut).

Basically make sure your jar is as clean as possible; chop up a little bit of cabbage, carrots, cauliflower, broccoli (any or all, this is just an easy beginner list, the possibilities are endless); jam it down in the jar leaving a good gap at the top, and packing it in to leave as little air as possible; top up with clean, salty water so the veggies are covered (not crazy loads of salt, but the water should taste like between blood and sea water) (can also use a weight to keep the veg submerged if necessary, like a clean glass with water in); cover, leave at room temp a few weeks; enjoy a delicious and healthy food that humans have maybe been doing since prehistory. I was going to say how it works, but ran out of time, look it up!

Do you have a bulk food store nearby? We have one where you can BYO containers, tare and label them, and then fill them up at the store. Bulk food with no bags or single-use containers, it's great.

Freezer bag sealing clips like Ikea's Bevara

My mom has a collection of old jars. I'm not sure even she knows what to do with them, but she's pretty crafty. Or if you're not super crafty yourself, maybe you know someone who is and would appreciate the jar? Idk.

Alternatively, you could recycle it. In my city there are a couple places people can take their recyclables (plastic, paper, glass, even yard waste) for free.

Just some thoughts: Spaghetti Lasagna Paintbrush with turpentine Tie wraps Paint rollers