Hi there, Sorry to be negative, but you'll be looking at alot more than 5 syns - the eggnog lattes are really quite naughty - I can't remember the exact syns but I know it's pretty much a days worth if not a bit more, a tall eggnog latte is 370 cals - compared to 100 for a tall skinny latte.
The eggnog is a really rich sweet mixture in a UHT box, and that's what they steam and add the espresso too, so you don't have the option of using a sugar free syrup or skimmed milk like with the other winter drinks, which means there is no way of making it any less naughty. TBH I wouldn't even use it as a HexA, and I often do that with my skinny lattes.
So unless you really love the eggnog lattes (I do! and can't believe i often used to have a huge venti eggnog latte , maybe even twice a day - almost as bad as mcdonalds milkshakes!) then aviod them or keep them as a rare treat.
HTH a little,
Amy x