Is it bad if i had 20-30g of added sugar in 2 weeks and then ate 100g in 1 day?

Don't worry about it.

Do you wish you hadn't eaten it, in other words, did you decide it wasn't worth it? If so, spend maybe 10 minutes (tops) thinking why it happened, and adjusting your going-forward plans so that it's less likely to happen in similar circumstances next time those circumstances happen, then let it go.

If it was worth it - like maybe you ate a slice of delicious birthday cake at your friend's birthday party, and had a wonderful time, and the cake tasted fabulous - just let it go. Keep that kind of thing quite rare, and everything will be fine.

One day is a drop in the ocean of life. Sugar (at 100g of it) isn't a poison. It's a food, and we need some food. It's a nutrient-sparse food, and can drive needed nutrition out of our day or put us over calories for that day, which isn't ideal, but it's not The End Of the World, or even the end of your transition to healthier calorie appropriate eating.

Just adjust your plan, and get back on a sensible track, everything will be fine. (You might see a little jump on the scale from water retention for a few days while that sugar gets metabolized, but that's not fat, and not worth worrying about. If it happens, it'll drop off when you've been back to your routine for a bit.)

You don't need to burn it off quickly. Just go on with life. If you happen to feel a little more energetic, some extra movement will just happen.

Put it this way: 70 extra grams of sugar is 280 calories. 280 calories is 0.08 (eight one-hundredths) of a pound of body fat, at most. If you ate 280 calories more than your maintenance calories that one day, the most you could've gained is 0.08 of a pound (0.036 of a kg). If you didn't eat over your current maintenance calories, you simply failed to lose that 0.08 of a pound that one day (true whether you were over/under your weight loss calorie goal, but under maintenance).

It's just not worth stressing over. Adjust your plan if needed, let it go.

It happens. Just get back on track tomorrow.