It appears in the literature...that glucose stimulates dopamine release:
http://cat.inist.fr/?aModele=afficheN&cpsidt=15007399

And that the inverse, is also true:
http://www.nature.com/npp/journal/v2.../1395477a.html

What appears to me is that this is a very complex question with very
complex answers. But basically it appears to me that the body has
ways to respond to metabolic changes. And since TS involves dopamine primarily, this would be affected.

Dopamine is a "reward" neurotransmitter... it signals pleasure. So we would be programed to respond to sugar with pleasure. In TS patients there is an error
in dopamine use and hence TSers react differently than others. But even in
non TS patients, sugar is alerting, and energy providing. I see people at work consuming Arizona Teas with 400 calories of SUGAR to get thru their day.
I drink water and eat a Detour or Zone bar for my snacks if I need them. ( I reserve a small amount of sugar for emergency use only, not as part of my daily diet intake). When I am very fatigued, and at the END of my rope, that is when I have a little sugar treat.
This is different than drinking sugar all day long, like some people I know, just to function at all.

The papers above are very hard to understand. And the reward aspect of dopamine is just becoming understood (based on the studies of methamphetamine abuse). Dopamine rewards video game players, and gamblers, and sexual attraction. Things that stimulate dopamine release, like amphetamines also cause tics. Sugar certainly falls into that category of "reward". Babies, will turn to sugar water more reliably than plain water. So that drive is present at birth. Many children without TS become very hyper on sugar consumption...this a common observation by many parents.

So high sugar would be affecting TS for some patients. Also the sudden drop in sugar levels then produce stress, which is also a dopamine releaser...so you are caught both ways!