From a taxation perspective, almost any employee perk is treated as if it were a payment, so there is little point for companies to create more paperwork.
IIRC, the main exceptions are
- use of a company car: it is assumed that the car will be shared between business and private use, different schemes exist how to calculate that split and only the "private" part is treated as income
- public transport subsidies: for employees without a company car, a metro pass can be substituted, a similar split-use assumption is made
- employee discounts: below a rather generous limit, these do not affect taxation of wages
- some financial products (in Germany, the term is "vermoegenswirksame Leistungen", quick googling suggests that Austria has similar provisions)
The latter is probably the most interesting to you, but also the most complicated from a taxation point of view. These do not need to be negotiated however, because you are already entitled to these and they are cost-neutral to your employer.
Pretty much any other perk will be treated the same as monetary compensation and it would be pointless to preallocate your salary in that way, from the employer perspective a gym membership is the same as asking for extra money and extra paperwork at the same time, and companies offering it are doing it mainly for reasons of "team building" or to reduce sick days.
