For me it’s:

9 looks like 0

0 looks like 9

5 looks like S

6 looks like b

starting a to-do list i guess

I've picked up a habit to (sometimes) write in all caps. On the flipside, I've picked up some strategies to differentiate letters and numbers from each other:

• 1 would have the top serif if it needs to be differentiated from lowercase l.
• 2 would start like a question mark, and then continuing on with a horizontal line, something like: ʔ︭
• 5 would be written in two separate strokes, the top one from left to right, and the second from top-left straight down, then a semi-circle going clockwise
• 6 would be written in one smooth stroke from top-right going counter-clockwise down, then up halfway, then intersecting itself at the bottom rather than bottom-left. (Kinda like φ)
• 7 would have the middle bar (differentiating it from a 1)
• 9 would have two strokes, first is a loop starting from top-right counter-clockwise almost meeting itself; second stroke goes from where the first one ends straight down-left-ish
• 0 would have a light stroke going from top-right to bottom-left
• D would be two strokes, kinda like this: |>
• I would have the top and bottom serifs
• J would have its top serif and its tail emphasized and angular, kinda like this: ˧˩̅ (I really hope the unicode characters show up properly)
• S would have its upper part smaller, and its lower part larger and more emphasized, so that it'd look more like a coiled snake.
• U would look like my lowercase u (with the right vertical downward stroke).
• V would be written in two strokes: top-left to bottom, and top-right to bottom.
• X is also written in two strokes: top-left to bottom-right, and top-right to bottom-left
• Z would optionally have the middle bar (Ƶ), but it usually doesn't need it to differentiate from 2