Saving is always an option. The CPI (Consumer Price Index, which is used to reflect inflation) for 2019 in Switzerland is 0.4%. Saving with a “Bonussparkonto” at bank WIR can yield up to 0.7% (provided you save more than 5,000.- a year and buy 25 shares of the bank (roughly 10,000.- with roughly 2.5% dividends).
Then you have term deposits, which I wouldn’t advise since the rates are very low. My Raiffeisen offers 0.4% for a 10 years term, for example.
For a time horizon longer than 10 years and assets meant to grow over a year of expenses (rough personal estimate), I’d still consider investing part of it (say 10% if you’re very conservative) in a fund of your choice (one single fund or robo-adivisory counsels, to keep it simple). People here will probably advise Degiro or IB, I’m using Vaud Kantonalbank’s TradeDirect because I’m investing in individual swiss stocks and want to be able to use the voting part of my shares and don’t mind paying extra fees for that (Swissquote would offer that too, I’ll have to investigate that option).
If you don’t want to risk loosing money and are willing to put in more than 5,000.- a year, the WIR Bonussparkonto is the best option in my opinion. The “buying shares” part is optional and carries a risk of going to zero but I don’t see it as very significant so I’d personally put 10,000.- in it to chase the better yields. Of course, your mileage may vary and if 10,000.- would be a significant part of your savings and you don’t want to risk them at all, you can skip it and settle for a 0.3% total yield (it was at 0.6% a few months ago so it might raise again if the situation regarding yields gets better).
Edit: if you have a mortgage, another option would be to pay it off, then dip in it again (or get a new one) when you need the money for your parents’ appartment. Paying off debt is a way of getting fixed interest on your money (by canceling negative interest) and as long as the collateral is still there and you still have a salary (assuming you do), increasing the mortgage (or getting a new one if you have written it off entirely) will still be an option to get liquidity when the need arises (that’s how my parents (and most other people of their generation where I live) have done it: live off your salary, buy a house, pay off the mortgage as a way to use your potential extra cash, live off AHV+2nd pillar in retirement).