If you carbonate it, that carbonation should give it a perceived fuller body. Aside from that, you could try adding some grape tannin or some acid blend, as those should help it feel fuller and more complex.
Here's a pretty decent primer from the Norther Brewer on basic cider making that covers these points in brief:
https://cdn.shopify.com/s/files/1/2785/6868/files/cider.pdf
On tannin addition:
OPTIONAL: Add tannin. Tannin helps the cider's "grip" and
structure. These are sensations more than flavors, but can
add wonderful complexity to the finished product. Start small,
as it doesn't take much to get the desired effect. Liquid or
dry tannin can be used to equal effectiveness. Remember,
it's always possible to add a little more, so err on the side of
caution.
On acid additions:
- OPTIONAL: Add acid. Most juice, especially juice made from
later season apples, will have a lot of sweetness, but little acid.
Acid helps to balance the cider by adding sharp, crisp character.
Small amounts of malic acid can be added to taste, up to
one tablespoon in five gallons. To ensure more accuracy and
repeatability, consider measuring the pH or using an acid titration
kit to determine approximate acid content. Remember,
it's always possible to add a little more, so err on the side of
caution.
There is a lot of other good general information in that pdf. If you plan on making more ciders, I think it's worth it to give it a quick read.