It’s a bit hard to tell in the pictures: is this a dual pane vinyl sliding window?

If it’s single pane (or single pane with a storm window) there isn’t a ton you can do. Most of the sound (and cold) will be coming though the glass. Anything you add will have a marginal improvement.

Assuming this is dual pane, there probably aren’t many place you’d be able to add weatherstrip that don’t already have some. So replacing any crushed/worn weatherstrip is one of the best things you could do.

Have you pinpointed exactly where drafts are coming through? You can use a candle/lighter to see where air is intruding. Oftentimes drafts are due to poor installation, and not necessarily the window construction.