For fingering weight yarn you can use size 8/0 or 6/0 or 'E' beads. A size 10 might work with the fingering or lace yarn; but they might be too small to show up on your sweater. However that depends on your pattern & how they contrast with the yarn. Makes no sense to go to the trouble of adding beads to your knitting, if the beads won't show up from a short distance. A size 6/0 is ideal; but try to find beads that have a shiny or sparkly finish that will show up & others will notice. If the beads are too close in color to your yarn, they could visually disappear into your stitches unless seen close up. The Japanese glass beads (Miyuki or Toho) are two high quality brands of glass beads. They are smooth on the inside & shouldn't damage your yarn. IMO, the finishes that give you a good sparkle/shine for your money are the AB (Aurora Borealis/Rainbow) & the Luster beads. Stay away from beads that are transparent on the outside with the color on the inside. The color may not be permanent & eventually wash away over time & wear. Also, the Galvanized metallic finish on beads (gold, silver, copper, etc.) is durable & the color is permanent as long as they are Miyuki's or Toho's. They are more expensive, though.
ETA: When adding beads, don't get carried away. When it comes to beads, less is more. Too many beads can make your item too heavy & the weight could stretch out your stitches over time. Too many beads can also be uncomfortable when sitting if you lean against a chair back or church pew. Just something to keep in mind.