Juice boxes, raisins/cranberries/other preferred dried fruit, dextrose tablets, dextrose gel. Funnily enough the last one seems to be the least effective for me...! I avoid sweets because I have sensitive teeth and and it hurts if I have too many (plus they're not the healthiest option - of course!). My mum used to carry around a jar of jam or honey (nowadays you could easily take a squeezy bottle of honey with you). For some reason golden syrup doesn't work well at all for me (I can eat like 10 spoonfuls and still be low half an hour later), but I know for some it's great. Also plain sugar works just great, and can be easily carted in a jar/pot. Obviously with some of these you kind of need a spoon though.